U.S. patent application number 13/267734 was filed with the patent office on 2013-04-11 for belt type continuously variable transmisson.
This patent application is currently assigned to Kawasaki Jukogyo Kabushiki Kaisha. The applicant listed for this patent is Seiji Itoo, Hideaki Kii. Invention is credited to Seiji Itoo, Hideaki Kii.
Application Number | 20130090199 13/267734 |
Document ID | / |
Family ID | 48019785 |
Filed Date | 2013-04-11 |
United States Patent
Application |
20130090199 |
Kind Code |
A1 |
Itoo; Seiji ; et
al. |
April 11, 2013 |
Belt Type Continuously Variable Transmisson
Abstract
A belt-type continuously variable transmission comprises a drive
pulley assembly mounted to a drive shaft; a driven pulley assembly
mounted to a driven shaft; a belt connecting the two; and a case
assembly for accommodating these components. The drive pulley
assembly has fins for generating a flow of air moving toward an
outer periphery of the drive pulley assembly. When viewed in an
axial direction of the drive shaft, an air blocking plate is
positioned at a forward side in a rotational direction of the drive
pulley assembly relative to an imaginary line segment connecting a
center axis of the drive pulley assembly to a center axis of the
driven pulley assembly, between the drive pulley assembly and the
driven pulley assembly such that the air blocking plate surrounds
the outer periphery of the drive pulley assembly over a
predetermined range.
Inventors: |
Itoo; Seiji; (Akashi-shi,
JP) ; Kii; Hideaki; (Kakogawa-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Itoo; Seiji
Kii; Hideaki |
Akashi-shi
Kakogawa-shi |
|
JP
JP |
|
|
Assignee: |
Kawasaki Jukogyo Kabushiki
Kaisha
Kobe-shi
JP
|
Family ID: |
48019785 |
Appl. No.: |
13/267734 |
Filed: |
October 6, 2011 |
Current U.S.
Class: |
474/93 |
Current CPC
Class: |
F16H 57/0416 20130101;
F16H 57/0489 20130101 |
Class at
Publication: |
474/93 |
International
Class: |
F16H 57/04 20100101
F16H057/04 |
Claims
1. A belt-type continuously variable transmission comprising: a
drive pulley assembly mounted to a drive shaft; a driven pulley
assembly mounted to a driven shaft; a belt wrapped around the drive
pulley assembly and the driven pulley assembly; and a case assembly
for accommodating the drive pulley assembly, the driven pulley
assembly, and the belt; wherein the drive pulley assembly has fins
for generating a flow of air moving toward an outer periphery of
the drive pulley assembly according to a rotation of the drive
pulley assembly; the case assembly includes a peripheral wall
portion surrounding the drive pulley assembly, the driven pulley
assembly, and the belt; and when viewed in an axial direction of
the drive shaft, an air blocking plate is positioned at a forward
side in a rotational direction of the drive pulley assembly
relative to an imaginary line segment connecting a center axis of
the drive pulley assembly to a center axis of the driven pulley
assembly, between the drive pulley assembly and the driven pulley
assembly such that the air blocking plate surrounds the outer
periphery of the drive pulley assembly over a predetermined
range.
2. The belt-type continuously variable transmission according to
claim 1, wherein when viewed in the axial direction of the drive
shaft, the air blocking plate is curved such that the air blocking
plate is gradually closer to the peripheral wall portion of the
case assembly in a forward direction of the rotational direction of
the drive pulley assembly and an inclination angle of the air
blocking plate with respect to the peripheral wall portion
decreases gradually.
3. The belt-type continuously variable transmission according to
claim 1, wherein the air blocking plate is integral with a
component of the case assembly.
4. The belt-type continuously variable transmission according to
claim 1, wherein the air blocking plate is independent of a
component of the case assembly and is mounted to the case
assembly.
5. The belt-type continuously variable transmission according to
claim 4, wherein the drive pulley assembly has fins on a surface at
one side in the axial direction of the drive shaft; and an annular
air guide plate having an air entrance on an inner peripheral
portion thereof is provided to face the surface of the drive pulley
assembly at one side in the axial direction of the drive shaft, and
the air blocking plate is provided integrally with the air guide
plate to extend along an outer periphery of the air guide
plate.
6. The belt-type continuously variable transmission according to
claim 1, wherein the peripheral wall portion of the case assembly
includes a drive-side peripheral wall portion surrounding a
substantially half of the outer periphery of the drive pulley
assembly, a driven-side peripheral wall portion surrounding a
substantially half of an outer periphery of the driven pulley
assembly, and an intermediate peripheral wall portion connecting
the drive-side peripheral portion to the driven-side peripheral
wall portion; and the driven-side peripheral wall portion is
provided with an air outlet which opens to face the outer periphery
of the driven pulley assembly and extends radially outward relative
to the driven pulley assembly such that the air outlet is tilted in
a forward direction of a rotational direction of the driven pulley
assembly.
7. The belt-type continuously variable transmission according to
claim 6, wherein the air outlet is provided to include a region
extending from an end portion of the driven-side peripheral wall
portion at a forward side in the rotational direction of the driven
pulley assembly to the intermediate peripheral wall portion
continuous with the end portion of the driven-side peripheral wall
portion.
8. The belt-type continuously variable transmission according to
claim 6, wherein the drive pulley assembly and the driven pulley
assembly are arranged in a forward and rearward direction; and the
air outlet is provided on an upper portion of the peripheral wall
portion of the case assembly.
9. The belt-type continuously variable transmission according to
claim 6, wherein the case assembly is provided with a rib for
guiding a flow of cooling air in a vicinity of the driven pulley
assembly to the air outlet.
10. The belt-type continuously variable transmission according to
claim 9, wherein when viewed in an axial direction of the driven
shaft, the rib is curved such that the rib is gradually closer to
the peripheral wall portion of the case assembly in the forward
direction of the rotational direction of the driven pulley assembly
and an inclination angle of the rib with respect to the peripheral
wall portion increases gradually.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a belt-type continuously
variable transmission incorporated into a vehicle. Particularly,
the present invention relates to a cooling structure of the
belt-type continuously variable transmission.
[0003] 2. Description of the Related Art
[0004] United States Patent Application Publication No.
2010/0167853 discloses a cooling structure of a conventional
V-belt-type continuously variable transmission (CVT) built into a
utility vehicle. In the continuously variable transmission
disclosed in this literature, a fixed sheave of a drive pulley and
a fixed sheave of a driven pulley are provided with fins which
function as centrifugal fans, and air introduced from outside into
a case is flowed through the drive pulley and then the driven
pulley, thereby cooling these pulleys and a V-belt.
[0005] An air-intake duct is mounted to the peripheral wall of the
case surrounding the drive pulley. Outside air suctioned through
the air-intake duct is guided to an air entrance closer to a center
of the drive pulley, and is blown toward the outer periphery of the
drive pulley as cooling air. Then, the cooling air is guided to an
air entrance closer to the center of a driven pulley by an air
guide member provided between the drive pulley and the driven
pulley, the cooling air is blown toward the outer periphery of the
driven pulley, and then the cooling air is discharged through an
air discharge duct which opens the peripheral wall of the case.
[0006] However, in the above conventional continuously variable
transmission, the flow of the cooling air blowing toward the outer
periphery of the drive pulley and the flow of the cooling air
blowing toward the outer periphery of the driven pulley interfere
with each other in a complex manner inside a narrow space of the
case. Therefore, it is difficult to form a flow of the cooling air
directed from the drive pulley toward the driven pulley as
intended.
SUMMARY OF THE INVENTION
[0007] The present invention addresses the above described problem,
and an object of the present invention is to improve an overall
cooling efficiency by flowing cooling air blowing toward the outer
periphery of a drive pulley assembly smoothly toward a driven
pulley assembly while suppressing interference with a flow of the
cooling air in the vicinity of the driven pulley assembly.
[0008] According to the present invention, a belt-type continuously
variable transmission comprises a drive pulley assembly mounted to
a drive shaft; a driven pulley assembly mounted to a driven shaft;
a belt wrapped around the drive pulley assembly and the driven
pulley assembly; and a case assembly for accommodating the drive
pulley assembly, the driven pulley assembly, and the belt; wherein
the drive pulley assembly has fins for generating a flow of air
moving toward an outer periphery of the drive pulley assembly
according to rotation of the drive pulley assembly; the case
assembly includes a peripheral wall portion surrounding the drive
pulley assembly, the driven pulley assembly, and the belt; and when
viewed in an axial direction of the drive shaft, an air blocking
plate is positioned at a forward side in a rotational direction of
the drive pulley assembly relative to an imaginary line segment
connecting a center axis of the drive pulley assembly to a center
axis of the driven pulley assembly, between the drive pulley
assembly and the driven pulley assembly such that the air blocking
plate surrounds the outer periphery of the drive pulley assembly
over a predetermined range.
[0009] In the above configuration, when the drive pulley assembly
and the driven pulley assembly start to rotate according to, for
example, the operation of the vehicle in the belt-type continuously
variable transmission, there is generated a flow of cooling air
moving toward the outer periphery of the drive pulley assembly, by
the fins, in the vicinity of the drive pulley assembly. The flow of
the cooling air is blown to the outer periphery of drive pulley
assembly. A part of the flow of the cooling air which is going to
collide against the flow of the air in the vicinity of the driven
pulley assembly adjacent to the drive pulley assembly, is blocked
by the air blocking plate, and flows in the rotational direction of
the drive pulley assembly in the vicinity of the drive pulley
assembly.
[0010] In this configuration, it is possible to suppress
interference between the flow of the cooling air generated in the
vicinity of the drive pulley assembly and the flow of the air
generated in the vicinity of the driven pulley assembly, and
intensify the flow of the cooling air in the vicinity of the drive
pulley assembly. The intensified flow of the cooling air moves
toward the driven pulley assembly along the peripheral wall portion
of the case assembly, and joins the flow of the air in the vicinity
of the driven pulley assembly smoothly. Therefore, cooling
efficiency of the drive pulley assembly, the driven pulley
assembly, and the belt can be enhanced.
[0011] The above and further objects, features and advantages of
the invention will more fully be apparent from the following
detailed description with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view showing an external appearance
of a utility vehicle according to an embodiment of the present
invention.
[0013] FIG. 2 is a perspective view of the utility vehicle, showing
an engine unit when viewed from rightward and slightly obliquely
rearward, in a state where a part of components are omitted from
the utility vehicle.
[0014] FIG. 3 is a perspective view showing the engine unit when
viewed from above, rightward and obliquely rearward.
[0015] FIG. 4 is a view showing a flow of cooling air in an
interior of a case of a transmission.
[0016] FIG. 5 is a cross-sectional view showing a structure of the
transmission.
[0017] FIG. 6A is a plan view showing a case body when viewed from
above.
[0018] FIG. 6B is a front view showing the case body when viewed
from forward.
[0019] FIG. 7A is a front view of an air guide plate provided
inside the case.
[0020] FIG. 7B is a cross-sectional view of the air guide plate
taken along B-B of FIG. 7A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereinafter, an embodiment of the present invention will be
described with reference to the drawings. Throughout the drawings,
the same or corresponding components are identified by the same
reference numerals and will not be described in repetition. The
stated directions are referenced from the perspective of a driver
riding in a utility vehicle.
[0022] FIG. 1 is a perspective view showing an external appearance
of the utility vehicle 1 (vehicle) according to an embodiment of
the present invention. For example, the utility vehicle 1 is
intended for four persons and has four wheels. The utility vehicle
1 includes a pair of right and left front wheels 2, a pair of right
and left rear wheels 3, a vehicle body frame 4, a driver seat 5, a
passenger seat 6, a left rear seat 7, and a right rear seat 8. The
front wheels 2 are suspended from the front portion of the vehicle
body frame 4, while the rear wheels 3 are suspended from the rear
portion of the vehicle body frame 4. The four seats 5.about.8 are
mounted on the vehicle body frame 4, and are arranged between the
front wheels 2 and the rear wheels 3 in a forward and rearward
direction.
[0023] The vehicle body frame 4 has a cabin frame (ROPS) 4a
surrounding a cabin for passengers. The driver seat 5 and the
passenger seat 6 are arranged side by side in a rightward and
leftward direction in a front-half portion inside the cabin which
is defined by the cabin frame 4a. Although the driver seat 5 is
located at the left and a steering wheel 9 steered by the driver is
disposed in front of the driver seat 5 in the present embodiment,
they may be located at the right. The left rear seat 7 and the
right rear seat 8 are arranged side by side in a rear-half portion
inside the cabin. A console box 10 is provided between the driver
seat 5 and the passenger seat 6, and positioned at a substantially
center region inside the cabin.
[0024] FIG. 2 shows an engine unit 11 of the utility vehicle 1 when
viewed from rightward and slightly obliquely rearward, in a state
where a part of the components such as the driver seat 5, the
passenger seat 6, the console box 10, etc., are omitted from the
utility vehicle 1. In the utility vehicle 1 of the present
embodiment, the engine unit 11 is accommodated into the console box
10. As shown in FIG. 2, the engine unit 11 is positioned at a
substantially center region inside the cabin. The engine unit 11 is
an assembly including an engine 12 and a transmission 13 which are
unitarily (integrally) coupled together. Although not shown, the
transmission 13 is coupled with propeller shafts, differentials,
etc., to allow a driving power of the engine 12 to be transmitted
to the front wheels 2 and to the rear wheels 3.
[0025] When viewed from above, slightly rightward and obliquely
rearward in FIG. 3, in the engine unit 11, the transmission 13 is
positioned at a right side of a crankcase 21 of the engine 12. As
described later with reference to FIG. 5, and others, a drive shaft
41 which is an input shaft of the transmission 13 is coupled to a
crankshaft 20 via a centrifugal clutch 26. At the right side of the
transmission 13, a fuel tank 14 (not shown in FIG. 2) is positioned
such that the fuel tank 14 is spaced apart from the transmission 13
to allow a transmission cover 34 to be detached for the purpose of
maintenance. In FIGS. 2 and 3, reference symbol 15 designates an
air-intake chamber disposed above the engine 12.
[0026] As shown in FIGS. 2 and 3, a case 30 (case assembly:
hereinafter referred to as a transmission case 30) of the
transmission 13 has a substantially elongated-circle shape when
viewed from the side. An air inlet 31 of a substantially
cylindrical shape protrudes from a front portion of a peripheral
wall extending along a periphery of the case 30 in a forward and
rearward direction and in an upward and downward direction, and a
rear end portion of an air-intake duct 22 is coupled to the air
inlet 31. The air-intake duct 22 extends forward inside the console
box 10 (see FIG. 1) and then is bent in front of a dash panel (not
shown). The air-intake duct 22 extends upward, and then its upper
end portion is curved rearward. After that, the air-intake duct 22
opens downward. Since the air-intake duct 22 opens at a relatively
high position in this way, it is possible to sufficiently suppress
rain water or muddy water from flowing into the air-intake duct
22.
[0027] An air outlet 32 protrudes from the rear end portion of the
upper portion of the peripheral wall of the transmission case 30,
and a lower end portion of an air discharge duct 23 is coupled to
the air outlet 32. The air discharge duct 23 extends upward, and
then is bent back in a vicinity of an upper wall of the console box
10 (see FIG. 1) inside thereof. Then, the air discharge duct 23
extends downward, and its lower end portion opens downward and
slightly obliquely rearward. In this way, since the uppermost
portion of the air discharge duct 23 is positioned substantially as
high as the console box 10, the rain water or muddy water is less
likely to enter the transmission case 30, after it has flowed into
the air discharge duct 23.
[0028] --Overall Configuration of Transmission--
[0029] Next, the structure of the transmission 13 will be described
in detail with reference to FIGS. 4 to 6. FIG. 4 is a view showing
a flow of cooling air in the interior of the transmission case 30.
FIG. 5 is a cross-sectional view showing the internal structure of
the transmission 13. FIG. 6A is a plan view showing a case body of
the transmission case 30 when viewed from above.
[0030] FIG. 6B is a front view showing the case body when viewed
from forward. Hereinafter, the forward and rearward direction, and
the rightward and leftward direction are referenced in the state
where the transmission 13 is incorporated into the utility vehicle
1.
[0031] As shown in FIGS. 4 and 5, in the present embodiment, the
transmission 13 is a V-belt-type continuously variable
transmission, and accommodates a drive pulley 40 (drive pulley
assembly) and a driven pulley 50 (driven pulley assembly) which are
arranged at the front and at the rear, respectively, inside the
transmission case 30 which is elongated in the forward and rearward
direction. As shown in FIG. 5, the drive pulley 40 is mounted to a
drive shaft 41 which is the input shaft, while the driven pulley 50
is mounted on a driven shaft 51 which is the output shaft. A V-belt
60 is wrapped around the pulleys 40 and 50. As described later, a
radius (effective diameter) of each of the pulleys 40 and 50 around
which the V-belt 60 is wrapped is changed, thereby changing a
transmission ratio continuously.
[0032] As shown in FIGS. 2 and 3 in addition to FIG. 5, the
transmission case 30 includes a body member 33 (hereinafter
referred to as a transmission case body 33) fastened to a crankcase
21 (reference symbol 21 appears only in FIG. 5) of the engine 12
such that a bottom wall portion 33a faces to the left, and a cover
34 (hereinafter referred to as a transmission cover 34) joined to a
right opening of the transmission case body 33. The transmission
case body 33 and the transmission cover 34 are made of, for
example, aluminum alloy, and a trim seal 35 (shown in only FIG. 5)
made of an elastic material intervenes between a portion of
transmission case body 33 and a portion the transmission cover 34
which are joined together. The transmission case body 33 has
peripheral wall portions 33b.about.33e extending vertically upward
at the right from the outer peripheral edge of the bottom wall
portion 33a, over the entire periphery.
[0033] When viewed from the right side, as shown in FIG. 4, the
peripheral wall portions 33b.about.33e have an elongated-circle
shape surrounding an elongated-circle defined by the drive pulley
40, the driven pulley 50 and the V-belt 60 with a predetermined gap
between them. To be specific, the peripheral wall portions include
the front wall portion 33b (drive-side peripheral wall portion)
having a substantially semi-circular shape and surrounding from
forward, a portion of the drive pulley 40 corresponding to about a
half of its periphery, along its outer periphery, the rear wall
portion 33c (driven-side peripheral wall portion) having a
substantially semi-circular shape and surrounding from rearward, a
portion of the driven pulley 50 corresponding to about a half of
its periphery, along its outer periphery, the upper wall portion
33d connecting the front wall portion 33b to the rear wall portion
33c, and the lower wall portion 33e connecting the front wall
portion 33b to the rear wall portion 33c (upper wall portion 33d
and lower wall portion 33e are a pair of intermediate peripheral
wall portions).
[0034] As shown in FIGS. 6A and 6B in addition to FIG. 4, the
cylindrical air inlet 31 protrudes forward from the front wall
portion 33b of the transmission case body 33. As described later,
according to the rotation of the drive pulley 40, air is suctioned
into an air entrance closer to a center of the drive pulley 40, and
thereby outside air is taken into the transmission case body 33
through the air-intake duct 22. The cylindrical air outlet 32 is
provided in a range from the upper end of the rear wall portion 33c
to the upper wall portion 33d continuous with the rear wall portion
33c in the transmission case body 33. As shown in FIG. 4, the air
outlet 32 is tilted upward and obliquely forward, and the air
flowing along the periphery of the driven pulley 50 is discharged
smoothly into the air discharge duct 23 as described later.
[0035] Turning back to FIG. 5, the bottom wall portion 33a of the
transmission case body 33 has a portion swelling inward
(rightward), in a front portion thereof corresponding to the drive
pulley 40, and a clutch cover member 33f is provided within a
dented portion formed at a back side (left side) of the swelling
portion to accommodate a centrifugal clutch 26 therein. The tip end
portion (right end portion) of the crankshaft 20 of the engine 12
penetrates the right side wall of the crankcase 21, protrudes into
the clutch cover member 33f and is joined to an inner member 26a of
the centrifugal clutch 26 such that the crankshaft 20 is rotatable
integrally with the centrifugal clutch 26.
[0036] The inner member 26a of the centrifugal clutch 26 is coupled
to a clutch housing 26c via a one-way clutch 26b. The clutch
housing 26c is rotatable integrally with the drive shaft 41 of the
transmission 13, and is rotatably supported on the inner peripheral
side of the clutch cover member 33f via a ball bearing 27.
Therefore, in a state where the centrifugal clutch 26 can transmit
a driving power, the rotation of the crankshaft 20 of the engine 12
(not shown in FIG. 5) is input to the drive shaft 41 via the
centrifugal clutch 26.
[0037] The rear portion of the bottom wall portion 33a of the
transmission case body 33, corresponding to the driven pulley 50,
is fastened to the rear portion of the right side wall of the
crankcase 21 of the engine 12 (not shown in FIG. 5). The driven
shaft 51 is rotatably supported on the right side wall of the
crankcase 21 via a ball bearing 28 in a state where the driven
shaft 51 penetrates the bottom wall portion 33a of the transmission
case body 33 and the right side wall of the rear portion of the
crankcase 21. Although not shown in the drawings, the left-half
portion of the driven shaft 51 protruding into the crankcase 21 is
the input shaft of a gear transmission mechanism, and the output
shaft of the gear transmission mechanism is coupled to propeller
shafts, differentials, etc., to transmit driving power to the front
wheels 2 and to the rear wheels 3.
[0038] --Drive Pulley--
[0039] The drive pulley 40 includes a fixed sheave 42 fixed to the
drive shaft 41, a movable sheave 43 fitted to the drive shaft 41
such that the movable sheave 43 is movable in an axial direction of
the drive shaft 41, and a sheave thrust generating mechanism 44 of,
for example, a flyweight type. As described above, one end portion
(left end portion) of the drive shaft 41 is mounted on the clutch
cover member 33f unitarily (integrally) with the housing 26c of the
centrifugal clutch 26 via the ball bearing 27. The opposite end
portion (right end portion) of the drive shaft 41 is mounted to a
boss portion 34a formed on the transmission case cover 34 via a
ball bearing 36. That is, the drive shaft 41 is supported by the
clutch cover member 33f of the transmission case body 33 and the
transmission cover 34 such that its both ends are mounted to the
clutch cover member 33f and the transmission cover 34,
respectively.
[0040] The fixed sheave 42 is fixed to the left end portion of the
drive shaft 41, while the movable sheave 43 is fitted to the drive
shaft 41 and positioned at the right side of the fixed sheave 42 to
face the fixed sheave 42 such that the movable sheave 43 is movable
in an axial direction of the drive shaft 41. The V-belt 60 is
retained on conical retaining surfaces of the sheaves 42 and 43.
When the movable sheave 43 moves on the drive shaft 41 and thereby
a distance between the movable sheave 43 and the fixed sheave 42
changes, the position at which the V-belt 60 is retained changes,
i.e., the effective diameter of the drive pulley 40 changes. As the
distance between the fixed sheave 42 and the movable sheave 43
decreases, the effective diameter increases, while as the distance
between the fixed sheave 42 and the movable sheave 43 increases,
the effective diameter decreases.
[0041] A receiver plate 46 of a rectangular frame shape is joined
to the back surface of the movable sheave 43 via a plurality of
coupling arms 45 extending to the right. The receiver plate 46 is
movable integrally with the movable sheave 43 in the axial
direction of the drive shaft 41. The above sheave thrust generating
mechanism 44 is provided between the movable sheave 43 and the
receiver plate 46. Although not explained in detail, for example,
the sheave thrust generating mechanism 44 is configured in such a
manner that a plurality of flyweights 44a rotate by a centrifugal
force in a direction indicated by an arrow S in FIG. 5, to press a
pressure-receiving roller 44b, and the resulting reactive force
causes the movable sheave 43 and receiver plate 46 to move to the
left (toward the fixed sheave 42). In brief, the sheave thrust
generating mechanism 44 generates a thrust to reduce a distance
between the fixed sheave 42 and the movable sheave 43 by using the
centrifugal force generated by the rotation of the drive pulley
40.
[0042] --Driven Pulley--
[0043] In the driven pulley 50, the fixed sheave 52 is fixed to the
right end portion of the driven shaft 51, while the movable sheave
53 is fitted to the driven shaft 51 and positioned at the left side
of the fixed sheave 52 to face the fixed sheave 52 such that the
movable sheave 53 is movable in the axial direction of the driven
shaft 51. For example, a cam tube 55 having a plurality of spiral
cam channels is attached to the outer peripheral surface of the
driven shaft 51, and the cam tube 55 and the fixed sheave 52 are
rotatable integrally with the driven shaft 51. A sleeve 56 is
unitarily (integrally) coupled to the inner peripheral end portion
of the movable sheave 53. The sleeve 56 is fitted to the outer
peripheral surface of the cam tube 55 such that the sleeve 56 is
movable in an axial direction and supports a roller (not shown)
movable along the cam channels of the cam tube 55.
[0044] The cam channels of the cam tube 55 have a spiral shape
extending to the right of the axial direction of the driven shaft
51 as it is closer to a forward side in a rotational direction of
the driven shaft 51. Because of this, when the movable sheave 53
receives a rotational force in the forward direction of the
rotational direction by a tension of the V-belt 60, a thrust acting
in the rightward direction of the axial direction is generated by a
cam action performed by the cam channels of the cam tube 55 and the
roller. The sleeve 56 is biased to the right (toward the fixed
sheave 52) in the driven shaft 51 by a pressure-adjusting spring
58. A pressing force is applied by the sleeve 56 to press the
movable sheave 53 against the fixed sheave 52, in addition to the
above thrust, thereby keeping a state where the effective diameter
of the driven pulley 50 is a maximum diameter as shown in FIG.
5.
[0045] In such a configuration, in the transmission 13, when the
speed of the rotation of the engine 12 input to the drive shaft 41
increases, and thereby the sheave thrust in the drive pulley 40
increases, a tension of the V-belt 60 increases, and a wedge force
of the V-belt 60 applied to the driven pulley 50 increases.
Thereby, the movable sheave 53 moves to the left in a spiral shape
along the cam channel away from the fixed sheave 52, against the
spring force applied by the pressure-adjusting spring 58 and the
cam thrust generated by the cam tube 55 and the radius of the
portion of the V-belt 60 which is wrapped around the driven pulley
50 decreases. As a result, a speed-reduction ratio of the output
rotational speed with respect to the input rotational speed
decreases, and a vehicle speed changes continuously from a
low-speed to a high-speed.
[0046] --Cooling Structure of Transmission--
[0047] As described above with reference to FIGS. 4, 6A and 6B, the
air inlet 31 is provided on the front wall portion 33b of the
transmission case body 33, and outside air is taken into the
transmission case body 33 through the air-intake duct 22. In the
transmission 13 of the present embodiment, to allow the outside air
to be taken into the transmission case body 33, a plurality of fins
42a are radially provided on the back surface (surface at one side
in the axial direction of the drive shaft 41, left surface in the
present embodiment) of the fixed sheave 42 of the drive pulley 40
and function as a centrifugal fan.
[0048] To be specific, as shown in FIG. 5, the plurality of fins
42a are provided on the back surface of the fixed sheave 42 such
that they are greater in height (i.e., height of the fins 42a from
the back surface of the fixed sheave 42) in a region closer to the
outer periphery. According to the rotation of the fixed sheave 42,
these fins 42a generate an air flow (indicated by an arrow in FIG.
4) in a direction from the inner periphery toward the outer
periphery. A circularly annular air guide plate 48 having a greater
outer diameter than the fixed sheave 42 is provided to face the
back surface of the fixed sheave 42 in close proximity to a portion
of the fins 42a which is closer to the outer periphery.
[0049] As shown in FIGS. 7A and 7B, the air guide plate 48 has a
substantially ring-shape formed by, for example, pressing a steel
plate by press forming. The air guide plate 48 has a substantially
circular opening 48a in a center region thereof. Three projections
48b are provided at the inner peripheral edge of the opening 48a at
substantially equal intervals along its periphery. Circular holes
48c open on these projections 48b, respectively. As shown in FIG.
5, bolts 49 are inserted into the holes 48c, respectively, to
fasten the projections 48b to the clutch cover member 33f of the
transmission case body 33.
[0050] At the left side of the air guide plate 48 mounted to the
clutch cover member 33f, an annular space is formed so as to
surround the clutch cover member 33f. The air inlet 31 opens to
face the space. The opening 48a in the center region of the air
guide plate 48 surrounds the clutch cover member 33f with a gap
between them, thereby forming an air entrance of a substantially
circularly annular shape. When the fixed sheave 42 rotates, the air
taken into the space through the air inlet 31 flows to a region
closer to a center of the fixed sheave 42 through the air entrance
and then flows radially toward the outer periphery of the fixed
sheave 42, as indicated by arrows shown in FIG. 5 (see FIG. 4).
[0051] The air (hereinafter also referred to as cooling air)
blowing toward the outer periphery of the fixed sheave 42, i.e.,
the outer periphery of the drive pulley 40, is directed to flow in
the forward direction of the rotational direction of the drive
pulley 40 by the front wall portion 33b of the transmission case
body 33, facing the front side of the drive pulley 40, and flows
downward along the front wall portion 33b. At the rear side of the
drive pulley 40, the flow of the cooling air blowing to the outer
periphery of the drive pulley 40 may collide against the air flow
in the vicinity of the driven pulley 50.
[0052] As a solution to this, in the present embodiment, in a
region where the flow of the cooling air blowing to the outer
periphery of the drive pulley 40 collides against the air flow in
the vicinity of the driven pulley 50 adjacent to the drive pulley
40 as described above, an air blocking plate 48d is provided within
a predetermined angular range so as to surround at least the outer
periphery of the fixed sheave 42 provided with the fins 42a, in the
outer periphery of the drive pulley 40. Although in the present
embodiment, the air blocking plate 48d is formed by bending the
outer periphery of the air guide plate 48 such that the air
blocking plate 48d and the air guide plate 48 constitute a unitary
member, as shown in FIGS. 5 and 7, an air blocking plate may
alternatively be mounted to the transmission case body 33
independently of the air guide plate 48, or otherwise, an air
blocking plate may be formed unitarily (integrally) with the
transmission case body 33.
[0053] As shown in FIG. 4, when the transmission case body 33 is
viewed from the right side in a state where the transmission cover
34 is detached (i.e., when the transmission case body 33 is viewed
in the axial direction of the drive shaft 41), the air blocking
plate 48d is positioned above (i.e., at a forward side in a
rotational direction of the drive pulley 40) an imaginary line
segment V connecting a rotational center of the drive pulley 40 and
a rotational center of the driven pulley 50 (center axis 41a of the
drive shaft 41 and center axis 51a of the driven shaft 51), between
the drive pulley 40 and the driven pulley 50, and has a
circular-arc shape surrounding the outer periphery of the drive
pulley 40 over an angular range of approximately 60 degrees to 70
degrees.
[0054] To be more specific, the lower end portion of the air
blocking plate 48d is positioned slightly above the imaginary line
segment V, and the air blocking plate 48d extends to be curved
upward and obliquely forward (in the forward direction of the
rotational direction of the drive pulley 40). The inclination angle
of the air blocking plate 48d with respect to the upper wall
portion 33d of the transmission case body 33 gradually decreases as
it is closer to the upper wall portion 33d. That is, the upper end
portion of the air blocking plate 48d (end portion at the forward
side in the rotational direction of the drive pulley 40) gets
closer to the upper wall portion 33d of the transmission case body
33 such that it is curved along the upper wall portion 33d.
[0055] Because of the above structure, a part of the flow of the
cooling air blowing to the outer periphery of the drive pulley 40,
which is blocked by the air blocking plate 48d, is caused to flow
in the forward direction of the rotational direction of the drive
pulley 40 along the air blocking plate 48d. Then, this cooling air
flow joins the cooling air flowing along the front wall portion 33b
of the transmission case body 33 as described above, and
intensifies the flow directed clockwise in FIG. 4 around the drive
pulley 40 as indicated by an arrow A1 in FIG. 4.
[0056] The intensified flow A1 of the cooling air moves around
substantially 3/4 of the periphery of the drive pulley 40 and then
toward the driven pulley 50 behind the drive pulley 40 along the
lower wall portion 33e of the transmission case body 33 as
indicated by an arrow A2. Then, the flow of the cooling joins the
flow of the air moving in the vicinity of a region below the driven
pulley 50. Since the driven pulley 50 has no fins, a relatively
weak flow of air moving in the forward direction of the rotational
direction of the driven pulley 50 is generated in the vicinity of
the driven pulley 50, but a strong flow of air moving to the outer
periphery is not generated. Because of this, the flow A2 of the
cooling air from the drive pulley 40 is not significantly
disturbed.
[0057] After the cooling air has joined the flow of the air in the
vicinity of the region below the driven pulley 50, it moves so as
to draw a curve, along the rear wall portion 33c from the lower
wall portion 33e of the transmission case body 33, in the forward
direction of the rotational direction of the driven pulley 50
(indicated by an arrow A3). After that, the cooling air is
discharged into the air outlet 32 provided in a range from the
upper end (end of the rear wall portion 33c at a forward side in
the rotational direction of the driven pulley 50) of the rear wall
portion 33c to the upper wall portion 33d continuous with the rear
wall portion 33c in the transmission case body 33. That is, the
flow A3 of the cooling air moves around substantially the half of
the periphery of the driven pulley 50, and the cooling air is
thereafter discharged.
[0058] The air outlet 32 is tilted upward and obliquely forward as
described with reference to FIG. 4 and others. In other words, the
air outlet 32 extends radially outward relative to the driven
pulley 50, from a portion thereof which opens to face the outer
periphery of the driven pulley 50 such that the air outlet 32 is
tilted in the forward direction of the rotational direction of the
driven pulley 50. Because of this, the flow A3 of the cooling air
moving in the forward direction of the rotational direction of the
driven pulley 50, in the vicinity of the driven pulley 50, is
discharged into the air outlet 32 smoothly.
[0059] Furthermore, in the present embodiment, to guide the flow A3
of the cooling air in the vicinity of the driven pulley 50, toward
the air outlet 32, as described above, a guide rib 33g is provided
on the bottom wall portion 33a of the transmission case body 33.
When the guide rib 33g is viewed from the right side as shown in
FIG. 4 (in the axial direction of the driven shaft 51), a
substantially lower half portion corresponding to an upstream side
of the flow of the cooling air is gently curved such that it
protrudes rearward so as to surround the center axis 51a of the
driven shaft 51, while a substantially upper half portion
corresponding to a downstream side of the flow of the cooling air
is gently curved such that it protrudes forward, differently from
the lower half portion.
[0060] The substantially upper half portion of the guide rib 33g
has a shape in which the inclination angle of the guide rib 33g
with respect to the upper wall portion 33d of the transmission case
body 33 increases gradually as it is closer to the upper wall
portion 33d gradually in the forward direction (i.e., in the
forward direction of the rotational direction of the driven pulley
50). Because of this, the flow of the cooling air moving in the
forward direction of the rotational direction of the driven pulley
50 in the vicinity of the driven pulley 50 is guided gradually
upward along the curved shape of the guide rib 33g, i.e., toward
the air outlet 32 of the upper wall portion 33d of the transmission
case body 33.
[0061] Since the air outlet 32 is provided in a range from the rear
wall portion 33c to the upper wall portion 33d in the transmission
case body 33, it is expected that warm air is discharged by
convection. To be specific, for a certain time period after the
utility vehicle 1 stops, and thereby the drive pulley 40 and the
driven pulley 50 stop their rotation, high-temperature air inside
the transmission case 30 moves upward naturally and is discharged
into the air discharge duct 23 through the air outlet 32.
[0062] --Operation of Transmission and Cooling Action--
[0063] Next, the operation of the transmission 13 in the utility
vehicle 1 of the present invention and the flow of the cooling air
associated with the operation will be described. In a state where
the engine 12 is in a stopped state or in an idle state, the
centrifugal clutch 26 is disengaged and therefore the drive shaft
41 of the transmission 13 is not rotating. At this time, the
movable sheave 43 of the drive pulley 40 and the receiver plate 46
are together in a right end position of the driven shaft 41, and
the movable sheave 53 of the driven pulley 50 is in a right end
position of the driven shaft 51 by the force applied by the
pressure-adjusting spring 58. Therefore, the transmission 13 is
placed in a state where the effective diameter of the drive pulley
40 is small and the effective diameter of the driven pulley 50 is
great, i.e., in a low speed-reduction ratio state.
[0064] When the engine speed increases and the centrifugal clutch
26 is engaged, the drive shaft 41 starts to rotate. At this time,
the driving power is transmitted from the drive pulley 40 to the
driven pulley 50 via the V-belt 60 with a low speed-reduction ratio
as described above. When the engine speed further increases, the
thrust generated in the sheave thrust generating mechanism 44
increases due to an increase in the centrifugal force in the drive
pulley 40, and causes the movable sheave 43 to move to the left in
the axial direction of the drive shaft 41. This reduces a distance
between the movable sheave 43 and the fixed sheave 42, and hence
increases an effective diameter of the drive pulley 40.
[0065] As described above, when the sheave thrust in the drive
pulley 40 increases, a tension of the V-belt 60 increases, and a
wedge force of the V-belt 60 applied to the driven pulley 50
increases. Thereby, the movable sheave 53 of the driven pulley 50
moves to the left in the driven shaft 51, against the spring force
applied by the pressure-adjusting spring 58 and the cam thrust
generated by the cam tube 55. As a result, a distance between the
movable sheave 53 and the fixed sheave 52 increases, and the
effective diameter of the driven pulley 50 decreases. Because of
the increase in the effective diameter of the drive pulley 40 and
the decrease in the effective diameter of the driven pulley 50, the
speed-reduction ratio of the transmission 13 decreases gradually,
and the vehicle speed increases.
[0066] As described above, according to the rotation of the drive
pulley 40 and the driven pulley 50, outside air is taken into the
transmission case 30 via the air-intake duct 22. The air cools the
drive pulley 40, the driven pulley 50, and the V-belt 60. The fins
42a provided radially on the fixed sheave 42 of the drive pulley 40
allow the fixed sheave 42 rotating to function as the centrifugal
fan, to move the outside air to the outer periphery of the drive
pulley 40 as described above.
[0067] As described with reference to FIGS. 4 and 5, the air
blocking plate 48d suppresses the flow of the cooling air in the
vicinity of the drive pulley 40 from interfering with the flow of
the air in the vicinity of the driven pulley 50. The cooling air in
the vicinity of the drive pulley 40 moves around substantially 3/4
of the periphery of the drive pulley 40 and then moves rearward
along the lower wall portion 33e of the transmission case body 33.
This flow of cooling air joins the flow of the air in the vicinity
of a region below the driven pulley 50. The resulting cooling air
moves around substantially half of the periphery of the driven
pulley 50 and thereafter is discharged into the air discharge duct
23.
[0068] That is, in the transmission 13 of the present embodiment,
the air blocking plate provided between the drive pulley 40 and the
driven pulley 50 suppresses interference between the flow of the
air in the vicinity of the drive pulley 40 and the flow of the air
in the vicinity of the driven pulley 50, and the flow (A1 shown in
FIG. 4) of the air in the vicinity of the drive pulley 40 is
intensified, thereby forming a main flow (A2) of the cooling air
directed toward the driven pulley 50. After the flow (A3) of the
cooing air moves around the periphery of the driven pulley 50, the
cooling air is discharged to outside the case. Therefore, the
overall cooling efficiency of the drive pulley 40, the driven
pulley 50 and the V-belt 60 can be enhanced.
[0069] In the present embodiment, since the driven pulley 50 has no
fins, unlike the drive pulley 40, only a relatively weak air flow
moving according to the rotation of the driven pulley 50 is
generated in the vicinity of the driven pulley 50. This makes it
possible to effectively suppress interference between the flow of
the cooling air in the vicinity of the driven pulley 50 and the
flow of the cooling air in the vicinity of the drive pulley 40
serving as the centrifugal fan. The fact that the driven pulley 50
has no fins has advantages that an increase in a friction
resistance of the air can be lowered and a driving loss can be
reduced.
[0070] The fact that the driven pulley 50 has no fins has an
advantage of cost reduction. In addition, in the present
embodiment, the air blocking plate 48d is provided unitarily with
the air guide plate 48 for guiding the cooling air to the air
entrance on the back surface of the drive pulley 40, which also
result in cost reduction.
Other Embodiments
[0071] The above embodiment is merely exemplary, and is in no way
intended to limit the present invention, its applications and uses.
Although in the transmission 13 of the present embodiment, the
drive pulley 40 and the driven pulley 50 are arranged at the front
and at the rear, respectively, for example, the present invention
is not limited to this. The two pulleys 40 and 50 may be arranged
in the upward and downward direction (vertical direction), or in
the rightward and leftward direction.
[0072] Although in the above described embodiment, the air inlet 31
and the air outlet 32 are provided on the transmission case body
33, at least one of them may be provided on the transmission cover
34. When the air inlet 31 and the air outlet 32 are provided on the
transmission case body 33 or the transmission case cover 34, it is
unnecessary to provide the air inlet 31 at the front portion
thereof and the air outlet 32 at the rear portion thereof as in the
above described embodiment.
[0073] For example, the air outlet 32 may be provided at the lower
portion of the rear wall portion 33c or the vertical center portion
of the rear wall portion 33c, instead of the upper portion of the
rear wall portion 33c, in the transmission case body 33. In any
case, the air outlet 32 is preferably tilted in the forward
direction of the rotational direction of the driven pulley 50, like
the present embodiment, but need not be tilted in this way.
[0074] Although in the present embodiment, the guide rib 33g for
guiding the flow of the cooling air in the vicinity of the driven
pulley 50 toward the air outlet 32 is provided unitarily with the
bottom wall portion 33a of the transmission case body 33, it may be
mounted to the transmission case 30 as a separable member, or may
be omitted.
[0075] The position, size, shape and the like of the air blocking
plate 48d disclosed in the present embodiment are merely exemplary.
Other positions, sizes, shapes and the like of the air blocking
plate 48d may be used so long as the air blocking plate 48d can
intensify the flow of the cooling air formed in the vicinity of the
drive pulley 40 and suppress interference with the flow of the air
in the vicinity of the driven pulley 50.
[0076] As described with reference to FIG. 4, for example,
desirably, the air blocking plate 48d is positioned at the forward
side in the rotational direction of the drive pulley 40 relative to
the imaginary line segment V connecting the center axis 41a of the
drive pulley 40 to the center axis 51a of the driven pulley 50,
between the drive pulley 40 and the driven pulley 50, and surrounds
the outer periphery of the drive pulley 40 over an angular range of
at least 45 degrees, when viewed in the axial direction of the
drive shaft 41.
[0077] In that case, the end portion of the air blocking plate 48d
at the forward side in the rotational direction of the drive pulley
40 may be distant from the peripheral wall portion (upper wall
portion 33d in the present embodiment) of the transmission case
body 33, or the end portion of the air blocking plate 48d at a
rearward side in the rotational direction of the drive pulley 40
may be positioned at the rearward side in the rotational direction
of the drive pulley 40 relative to the imaginary line segment
V.
[0078] In the present embodiment, the driven pulley 50 has no fins,
to prevent a strong air flow from being generated in the vicinity
of the driven pulley 50. The present invention is not limited to
this, and the driven pulley 50 may have fins so long as it does not
disturb the flow of the cooling air from the drive pulley 40.
[0079] Although in the present embodiment, the belt-type
continuously variable transmission 13 incorporated into the utility
vehicle 1 has been described, the transmission 13 may be
incorporated into vehicles such as ATVs (all terrain vehicles) or
motorcycles, for example, as well as utility vehicles. These
vehicles may be hybrid vehicles or electric vehicles rather than
gasoline vehicles.
[0080] As this invention may be embodied in several forms without
departing from the spirit of essential characteristics thereof, the
present embodiments are therefore illustrative and not restrictive,
since the scope of the invention is defined by the appended claims
rather than by the description preceding them, and all changes that
fall within metes and bounds of the claims, or equivalence of such
metes and bounds thereof are therefore intended to be embraced by
the claims.
* * * * *